You right click on the picture you want to use. Then put the image tags around it.

So it'll look like this

[IMG]properties[/IMG]

here's it with the signature alyssa made you

[IMG]http: //img.photobucket.com/albums/v708/bobbernut/Siggies/Screechladysig.gif[/IMG] (just remove the space after http: )

Or you should save the picture first to your account (photobucket??), then you can right click, get the properties, copy and paste them between the img tags.